Rectifier.



PATENTED MAR. 17, 1903.

E. THOMSON.

K RECTIFIER.

APPLICATION FILED D110.v 15, 1898.

2 SHEETS-SHEET 1.

'10 MODEL.

mz' NORRIS vcrzns co. PmTo-umu. WASHINGTON, 0 c.

UNITED STATES- PATENT OFFICE.

ELIHU THOMSON, OF SWAMPSCOTT, MASSACHUSETTS,- ASSIGNOR TO THE GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

RECTIFIER.

SPECIFICATION forming part of Letters Patent No. 723,07 6, dated March17, 1903. Application filed December 15, 1898. Serial No. 699,351. (Nomodel.)

To all whom it may concern/.2 1

Be it known that I, ELIHU THOMSON, a citizen of the United States,residing at Swampscott, in the county of Essex and State .ofMassachusetts, have invented certain new and useful Improvements inRectifiers, (Case No. 875,) of which the following is a specification.

In order to obviate or reduceto a minimum the amount of sparking whichmay take place in the operation of rectifying devices for changing analternating current of any particular character to a'unidirectionalcurrent, it is necessary that the commutation or periodic disconnectionof the alternating mains from the work-circuit carrying theunidirectional current should take place at such points in the wave ofthe alternating current orcurrent-s as will result in the smallest valueof unbalanced electromotive force acting between the terminals of therespective circuits as they are being separated. If the relativepositions of the commutator and brushes of the rectifying device at theinstant of commutation beara fixed relation in point of time to someparticular phase value of the impressed alternating electromotive force,it' will be evident that as the load changesin the work-circuit theinstant at which come mutation takes place will occur at differentpoints or values in the current-wave, owing to the fact that the changein impressed electromotive force, or effective resistance of thework-circuit, produces a changein the phase relations between theimpressed alternating electromotive force and current, wherefrom itfollows that if the brush adjustment in the rectifying device besuitable for one particular load it becomes unsuitable fora differentload or loads. I have discovered that by automatically varying the timesat which commutation takes place in accordance with varying load suchrelations-may be maintained between the electromotive forces acting atthe instant of commutationas will result in a minimum amount of sparkingof the rectifying device through its entire range of opera-v tion. Iconsider myself the first to devise means for accomplishing this result,and I intend hereinafter to lay claim to the same broadly.

Although in the following description and accompanying drawings I haveset forth an arrangement of apparatus suitable for carrying out myinvention, it will be evident that my invention in its broader aspectsis notin any sense limited to the employment of the particular apparatusshown, but may be em-- bodied in and its beneficial results obtainedfrom the employment of many similar arrangements, whether the same be intheir action electrical or largely mechanical. In short, my in veniioncomprises the broad idea of causing the operation of commutation in arectifying device to be automatically made at such variable instantswith respect to the phase of the impressed electromotive force as may benecessary to secure a minimum amount of sparking with changes of load.

The brushes and commutator of a rectifying device such as I employ arerelatively movable with respect to each other; but so far as myinvention is concerned either of them may be fixed in space and theother movable with respect thereto, the adjustment between the samebeing performed in any desired manner, one method of doing which I havehereinafter shown.

In the drawings, Figure 1 illustrates in diagram a rectifying devicesupplied with constant current and operating in accordance with myinvention, the constant current being derived from the secondaries oftwo-phase constant-current transformers. .trates a similar arrangementapplied in connection with three-phase apparatus. Fig. 3 shows a systemin which a plurality of rectifying devices are operated from the samedistributing-mains- Figs. 4 and 5 represent a plurality of commutatingdevices mechanic ally geared together, so as to maintain a constantratio between their relative rates of rotation. Fig. 6 illustratesdiagrammatically a switching-over apparatus for putting a workcircuit inconnection with any one of a plurality of rectifying-circuits, and Fig.7 illustrates one form of brush-actuating mechanism which may beemployed in carrying out my invention.

The alternating currents to be rectified may be derived from anysuitable source, whether single-phase or multiphase and whether gen-Fig. 2 illus- ICO erated in that form directly or converted into thatcharacter by suitable transforming apparatus.

In Fig. 1 l have illustrated a two-phase generator A, from which thecurrent to be rectified is derived. So far as my invention is concernedthe construction of the generator is immaterial; but it is preferably ofthe direct-driven slow speed multipolar type now commonly employed. Thegenerator has the usual revolving field F, connected, throughcollector-rings, with the exciter E for furnishing current thereto. Thestationary member of the generator carries two sets ofangularlydisplaced windings in which currents differing in phase byninety degrees are'induced. These windings are interconnected in theordinary manner, and mains m are connected thereto and lead to adistribution system from which current may be derived for any desiredpurpose, such as operating motors, lights, or other translating devices.From the distributing-mains m m connections are made to the primarycoils P I of a constantcurrent transformer of the type operating bymutual repulsion of the primaries and secondaries of the same. Therelative motion between the primary and secondary windings of atransformer of this type incident to changes of load in the circuitsupplied by the secondary windings of the same is utilized to suitablyshift the brushes, which operate in connection with the rectifyingdevice for changing the secondary alternating current into aunidirectional current. The movable secondary coils of the transformerare shown at S S The core of the transformer is indicated in dottedlines. The secondary coils, as before stated, are relatively movablewith respect to their respective primary coils, and in order to make themovement of each coil even, as well as dependent upon the movement ofthe other, I mount the said secondary coils in connection with somesuitable system of mechanical devices whereby the movement of onesecondary coil toward its primary is communicated to the other secondarycoil in such manner as to produce a similar movement of the latter coil.

In Fig. l I have shown one arrangement of apparatus for accomplishingthis purpose,the same consisting of balancing-levers L L L to which thesecondary coils are connected by flexible or link connections, as shown.The levers L L L referred to are separately mounted, so as to turn aboutthe rod 00 as a fulcrum, or they may, if desired, be arranged onknife-edges, as may be preferred, the particular construction being amere matter of mechanical detail. One end of the lever L supports oneside of the secondary coil S, while'its opposite end supports one sideof the other secondary coil S The other ends of the respective secondary(-oils S S are supported through suitable connections from the opposingends of the two levers L L ,as shown. These connections are so made andadjusted that the Weight of the secondary coil S overbalances that ofthe secondary coil S, with the result that when there is no currentflowing the respective secondaries S S are brought closely adjacent totheir respective primaries. It will be observed that the downward pulldue to the secondary S acts through the chain C- and lever L to raiseone end of the secondary coil S, while the downward pull exerted by thesecondary S on its supnorting-chains C G acts through the levers L L toraise the opposite end of the secondary S. As regards the operation ofthis transformer it will suffice for the present purpose to state thatas the resistance in the secondary circuit increases the currentsupplied thereto consequently tends to decrease,with the result that thesecondary coils approach their respective primary coils, being no longerrepelled by the same force as before. By this action the flux throughthe secondary coils is increased, thus causing an increase in secondaryelectromofive force, and so tending to preserve a constant current inthe secondary.

Thecurrentsin the transformer-secondaries are conducted by suitableleads to a rectifydevice K. The rectifying device may be directlymounted on the shaft of the prime mover, or it may be suitably gearedthereto, as shown, or it may be driven by a synchronous motor, as may bedesired. Suitable contact-rings R, carried upon the shaft of the commutating device and insulated therefrom and from each other, areconnected to the respective terminals of the secondary windings, asshown. Each ring in its turn is connected to the corresponding segmentsof a two-phase commutator, similar to the commutator in the Brusharc-lighting machine. One set of commutator-segments is connectedthrough the corresponding rings R with one of the secondary coils of thetransformer. Another set of commutator-segments, angularly displaced onthe same shaft carrying the first set, is connected through other ringswith the other second ary coil. The breaks in one commutator comeopposite the middle points in the conducting portions of the other commutator. As the present invention has no special reference to theparticular form of commutator employed, a more detailed description ofthe same is unnecessary.

Brushes B B, carried by a suitable yoke Y, bear upon the commutators,each brush making contact simultaneously with each commutator, as shown.The yoke Y is arranged to be rotated through a limited are about theaxis of rotation of the commutator in order to secure the properadjustment necessary to a sparkless operation of the same, as has beenexplained. In order to render this adjustment automatic with changes ofload in the work-circuit, suitable mechanical connections are madebetween the yoke Y and the moving secondaries of the transformer thecurrents from which are to be rectified. Many suitable devices foraccomplishing this purpose maybe produced, and in i Fig. 1 I have shownone arrangement which I have found desirable. This arrangement consistsof the lever L fulcrumed at some fixed point, as p, and connected froman intermediate point of the same to the yoke Y by the link L The freeend of the lever L is connected by the link L with some one of theoscillating levers L L U-as, for example,the lever L In the operation ofthese mechanical connections it will readily be seen that thereciprocating motion of the secondary coils S S of the transformerconsequent upon changes of load in the circuit supplied thereby istransformed into an oscillating motion and is communicated to the yokeY,carrying the brushes B. By proper attention to the mechanical designof this structure the motion communicated to the yoke Y may be made suchas to shift the brushes B backward and forward as the load changes insuch a manner as will result in a minimum amount of sparking at thecommutator. It is obvious that the motion of the secondary coils may becommunicated to the brushes B in any other manner than that shown,either directly or indirectly, as found most convenient.

In Fig. 2 I have shown an apparatus for rectifying threephase currents,the device for performing this function being somewhat difierent fromthe arrangement of apparatus shown in Fig. 1. A three-phase generator AY or any other source of three-phase current is used to supply energy tothe three-phase constant-current transformer, such as shown in Fig. 2.Three primary coils P P P are interconnected in the usual manner andreceive their energy through leads m of the threephase system. It isevident, of course, that the three-phase currents in the mains m may besupplied to any other translating devices desired without involving anydeparture from my invention. Associated with the primary coils of thetransformer are corresponding secondary coils S S S, mounted upon asuitable framework G and movable relatively to the primary coils. Bothprimary and secondary coils encircle suitable legs or branches of thetransformer-core. (Shown in dotted lines.) The frame G is connectedthrough suitable cross-bars and uprights with one end of the lever L,the connections with the lever being made by means of the shaft H,movable within an opening in said lever. The lever L is fulcrumed in asuitable manner at p, and the weight of the secondary coils of thetransformer is nearly but not quite balanced by the weight W, arrangedto slide on one arm of the lever L. Currents from the secondary coilsare transmitted through suitable conductors to brushes bearing upon thecollectorringsRof the rectifying device K, which may be driven in anywell-known manner. The rings are respectively connected to the segmentsof the commutator for rectifying the three-phase current. The rectifiedcurrent is collected by brushes ]3 and transmitted to the same shaft.

the work-circuit supplying arc-lamps or the like. The brushes B,similarly to the construction shown in Fig. 1, are carried by a yoke Y,the latter being connected, as shown, by a link L to some convenientpoint in the length of the lever L. The repulsion of the secondary coilsof the transformer by the primaries acts, as in the form shown in Fig.l, to communicate motion through the lever L to the yoke Y, and so toadjust the position of the brushes B. By suitable proportioning and adjnstment of parts the brushes B may be maintained in the position ofminimum sparking throughout the limits of load variation of theapparatus. It is obvious that the arrangement of levers shown might beradically varied without in any way departing from the principle of myinvention.

Fig. 3 indicates diagrammatically a plurality of rectifying-commutatorshaving a fixed ratio of rotation-such as would be obtained, for example,by mounting them upon The brush-carrying yokes Y and Y are actuated inthe manner previously described, the movements of the secondary coils SS actuating the yoke Y of one commutator and the movements of the set ofsecondary coils S S actuating the yoke Y of the other commutatingdevice, the primaries corresponding to these secondary coils beingexcitedfrom the same distribution system, as shown. A

Instead of mounting the respective rectifying sets on the same shaft itis equally feasible to mount each set upon a separate shaft, theindividual shafts being connected by suitable gearing, such asspur-wheels or other positively-acting devices of an appropriate nature,for maintaining a fixed ratio of rotation between the individualrectifyingcommutators, as shown in Fig. 5.

Where rectifying apparatus is to be operated continuously, or at leastthroughout long intervals, as in commercial practice, it is advisablefrom motives of prudence to follow the common engineering practice ofproviding reserve sets of apparatus to take the place of the apparatusin use in the event of injury or accident to the same, thus obviatingotherwise vexatious and annoying delays in service. In the employment ofreserve apparatus itis desirable to provide change-over switches forsubstituting the connections of the reserve apparatus for those of theapparatus to be cut out of circuit. In Fig. 6 I have illustrated anarrangement of switches and circuits for accomplishing this result. Themains supplying the alternating current to be rectified are shown at mand two sets of connections are taken therefrom, one set of which may beput in circuit with the mains m through the switch X, while the otherset of connections may in similar manner be put in circuit with themains m through the switch Z. The circuit m is intended to supply theprimary of the transformer, the secondary of which supplies current tothe rectifying device K. In similar manner the circuit m supplies theprimary of the transformer, the secondary of which furnishes current tothe rectifying device K The switch Z isintended to connect either one ofthe two commutating devices K K with the workcircuit-supplying lamps L.The switches X Z Z are mechanically connected in some suitable manner soas to be operated simultaneouslyas, for example, by the connecting-barb.

As the connections are shown in Fig. 6 the rectifying device K isconnected through its transformer (not shown) with the mains m andthrough the switch X with the distributing-conductors m. The commutatorof the rectifying device K is connected through the switch Z with thework-circuit, as shown. In case of accident to the set of apparatus thusin circuit the switches X Z Z may be thrown, thus cutting out thisapparatus and putting in circuit the rectifying device K with itssimilar set of supply devices, as will be readily understood.

. Instead of shifting or adjusting the brushes of the rectifyingapparatus through motion derived from the repulsion of the windings ofthe main supply-transformer I sometimes prefer to employ a device thepurpose of which is primarily to operate the brush-shifting mechanismand not to operate as a transformer, as in the cases above described. InFig. '71 have illustrated such an arrangement of apparatus. The primaryand secondary of a supply-transformer are shown at P and S and. may beeither relatively movable or fixed with respect to each other, as may bedesired. If the coils are movably related to each other, the weight ofone of the coils may be partially counterbalanced by means of a leverand suitable connections with the weight W, as diagrammaticallyindicated. At Z is illustrated the actuating mechanism for adjusting thebrushes of the rectifying device K. This device consists of tworelatively movable coils, the force exerted between which iscommunicated through suitable levers and links with the brush-carryingyoke Y. Through one of the coils the current from the secondary S of themain transformer passes, while through the other coil is passed thecurrent from the primary P of the main transformer. It will thus be seenthat the force exerted between the relatively movable coils of theactuating device is dependent upon the load supplied by the maintransformer. By suitable proportioning and arrangement of parts therelative motion of the coils of the brush-shifting device may be sotransmitted to the brushes of the rectifying commutator K as always tomaintain the same in a position of minimum sparking. If found desirable,the coils of the brush-actuating device may be associated with a core ofmagnetic material. (Indicated in dotted lines.)

Although in the apparatus above described I have illustrated constant-current transformers, because of the desirability of obtaining arectified current of constant volume suitable for use in supplyingarc-lights or the like, it will be evident that my invention is not tobe limited to the employment of such transformers, for, if founddesirable, I may employ any other type of transformer, or, indeed, I maydispense with the use of transformers altogether. In cases where I donot make use of constant-current transformers of the type described Imay substitute for their function as brush-shifting devices any othermechanism suitable therefor, since it will be understood that myinvention in its broader aspects is not dependent upon the particularmeans employed for maintaining a sparkless relation between the parts ofthe rectifying device when in operation.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is

1. The combination of conductors carrying alternating currents, arectifying-commutator and brushes, and means for automatically causing agiven relative position of commutator and brushes to occur atnon-corresponding points in succeeding waves of the impressedalternating electromotive force.

2. The combination of mains carrying alternatingcnrrents, a rectifyingdevice for changing the alternating currents into unidirectionalcurrents and means for automatically causing the times of commutation tovary with respect to the phase of the impressed alternatingelectromotive force.

3. The combination of conductors carrying alternating currents, arectifying device for changing the alternating currents intounidirectional currents, and means for automatically causing therectification to take place corresponding to varying phase values of theimpressed alternating electromotive force.

4. The combination of mains connected to a distribution system andcarrying alternating currents, a rectifying device for changing thealternating currents into unidirectional currents, andautomatically-controlled means for maintaining such a relation betweenthe phase of the current to be rectified and the instants whenrectification takes place as will result in a substantially non-sparkingoperation of the rectifier.

5. The combination of mains connected to a distribution system andcarrying alternating currents, a rectifying device for changing thealternating currents into unidirectional currents, and automatically-controlled means for maintaining brushes of said rectifyingdevice in the position of minimum sparking as the power of saidalternating current varies.

6. The combination of a transformer having coils relatively movable withrespect to each other, a rectifying device receiving current from one ormore of said coils, and means controlled by the relative movement ofsaid coils for varying the times at which rectification takes place.

7. The combination of a transformer having coils relatively movable withrespect to each other, a rectifying commutator and brushes, and meansoperated by relative movement between said coils to shift the positionof the brushes on the commutator.

8. The combination of a transformer having coils movable relatively toeach other, a commutator, ayoke carrying brushes bearing on saidcommutator and a system of link-andlever connections between said yokeand one of said coils.

9. The combination of a transformer having coils movable relatively toeach other, a commutator, brushes bearing thereon and mechanicalconnections between said brushes and one of said coils.

10. The combination of a plurality of transforming devices adapted toreceive current of one character and to deliver said current in analtered condition, mains for supplying current to said devices, andsimultaneously-operated switches with suitable connections for cuttingone of said devices out of circuit and replacing it by'another of saiddevices.

11. The combination of a plurality of pairs of collector-rings, one pairfor each phase of a polyphase current; at least one commutator-segmentfor each collector-ring; a motor operating the rings and commutators;brushes for the collector-rings; and brushes for the commutators, allsubstantially as set forth.

In witness whereof I have hereunto set my hand this 12th day ofDecember, 1898.

ELIHU THOMSON.

Witnesses:

DUGALD MOKILLOP, JOHN McMANUs.

